I never found cranberry juice was in the least helpful for me. I've said it before in another thread but the ONLY thing I found that works apart from antibiotics is D-Mannose (which is actually found in cranberry but you'd need rather a lot to be effective - d-mannose is a pure plant sugar but NOT ordinary sugar)
. It adheres to the e-coli bacteria in the bladder, preventing them stick to the bladder wall. Then you flush them out. No resistance, no side-effects. It works, but it's not cheap and you have to get it online. I never go anywhere without a little bag of white powder and I take a spoonful twice a day in water as a preventative because I've always been prone to getting UTIs.
Cytospurin won't disable bacteria, just make the symptoms more bearable temporarily.
I recommend this book:
The Patient's Encyclopaedia of Cystitis, Sexual Cystitis, Interstitial Cystitis by Angela Kilmartin
as an excellent guide to good bladder hygiene and practice, but I would highly recommend trying d-mannose. It works for infections caused by e-coli, which most UTIs are.